3D Printing Advice

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1

I have been dealing with an annoying problem with my Ender 3 V2 and I feel this is a common occurrence for any machine. Whenever I begin a new GCODE/print and the hotend and bed are heating up, the hotend eventually gets hot enough that it just oozes a string of plastic for a bit. Seeing how the extruder is not moving, I can only imagine there is some sort of pressure inside the hotend that pushes out the plastic for a bit.

Once it is done heating up, it drags this string of filament all around and often interferes with the first print layer. I often start prints from work and am not around to remove the string before it begins printing. I can see with a camera and stop the print if needed but its frustrating to say the least.

Is there any workaround for this issue? Any settings I should change to prevent this?

2

Not being around when the print starts limits your options considerably. I usually just take a shop towel and wipe off the ‘drool’ when it’s getting close to print temp, trying to do that remotely sounds like it might well be more trouble than it’s worth.

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3

A few things you can do

  1. In your ending gcode, retract a few mm of filament. It will remove some pressure before it cools.
  2. You can accept some gcode to purge the nozzle first. I have it print a 100mm line on the front edge of the print bed as part of my startup sequence.
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4

I end my prints with a 5mm retract, that usually takes care of it for me. You will need to also start with either a 5mm extrude or make sure your priming path is long enough.

5

I normally print a skirt. That seems to take care of any excess or retraction issues by the time it’s done printing the skirt.

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6

I also include a “purge” or “prime” line in my start gcode on all prints. My build platform takes longer to heat than the extruder, so I preheat the extruder to a temp below when it starts to ooze while the bed heats up. I want the bed at temp before doing my ABL bed tilt check. My printer can move the nozzle beyond the edge of the build platform, so I move off the platform for the final extruder heat so that the drool is trimmed off when the nozzle comes back on to the platform. Then the prime line makes sure the hot end is full and ready to start the real print.

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This is all great advice. I do have a prime line up the left side of the bed before each print and that will often take care of it. I also print with a skirt to clear the nozzle even more. Its just sometimes it likes to drop its “drool” off right in the middle of my bed. I like Toms idea of heating up outside the print bed and then moving over the bed and trying to “clip” it off. I am not sure if the Ender 3 has that type of geometry or not, I will need to check later.

I will have to implement the retract 5mm at the end of my GCODE and see if that helps. I like that idea too.

Thanks everyone

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Even if you can’t get off the bed, having the pre-heat happen near the start of the prime line will prevent the ooze from ending up in the middle of the bed.

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9

From experience I can tell you that not all of the previous suggestions will work 100% of the time. There are other variables that prevent some of these solutions from always working.

I will tell you what my Prusa Mk3s with MMU2s does and how it works out. Because its a great example of what works and what doesn’t.

At the end of every print job they include Gcode that will unload the filament completely. It rams the filament back and forth into the hot end a few times at tested speeds to form a spear shaped tip on the filament. Then it retracts all the way back into the MMU2s. So there is no filament left in the nozzle except for some residue.

At the start of a print they…

  • Turn on the heated bed
  • Raise the Z a little
  • Home X and Y
  • Heat the nozzle

Depending on the filament I used previously it will still ooze a little. Even though it has no pressure and the nozzle is mostly empty. I use a lot of PETG and it oozes every time. PLA usually doesn’t ooze much at this point.

  • Home Z
  • Perform a bed mesh leveling (All the while the little ooze is getting dragged around)
  • Then they print a line they call the purge line or prime line. That is where the ooze always gets caught. But the purge line they do starts with a bit of a blob at the beginning. It causes the filament to puddle up around the nozzle a bit before they start moving. That way it cleans the nozzle.

I can share the Gcode if anyone wants.

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10

Thanks for advice Aaryn! I’m gonna play around with my start and end gcodes to see if i can get a good sequence of events to prevent or minimize this oozing effect.

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